invoke.texi (Wsuggest-final-types, [...]): Document.

	* doc/invoke.texi (Wsuggest-final-types, Wsuggest-final-methods): Document.
	* ipa-devirt.c: Include hash-map.h
	(struct polymorphic_call_target_d): Add type_warning and decl_warning.
	(clear_speculation): Break out of ...
	(get_class_context): ... here; speed up handling obviously useless
	speculations.
	(odr_type_warn_count, decl_warn_count): New structures.
	(final_warning_record): New structure.
	(final_warning_records): New static variable.
	(possible_polymorphic_call_targets): Cleanup handling of speculative info;
	do not build speculation when user do not care; record info about warnings
	when asked for.
	(add_decl_warning): New function.
	(type_warning_cmp): New function.
	(decl_warning_cmp): New function.
	(ipa_devirt): Handle -Wsuggest-final-methods and -Wsuggest-final-types.
	(gate): Enable pass when warnings are requested.
	* common.opt (Wsuggest-final-types, Wsuggest-final-methods): New options.

	* g++.dg/warn/Wsuggest-final.C: New testcase.
	* g++.dg/ipa/devirt-34.C: Fix.

From-SVN: r213518

gcc/ChangeLog

+2014-08-01  Jan Hubicka  <hubicka@ucw.cz>
+
+	* doc/invoke.texi (Wsuggest-final-types, Wsuggest-final-methods): Document.
+	* ipa-devirt.c: Include hash-map.h
+	(struct polymorphic_call_target_d): Add type_warning and decl_warning.
+	(clear_speculation): Break out of ...
+	(get_class_context): ... here; speed up handling obviously useless
+	speculations.
+	(odr_type_warn_count, decl_warn_count): New structures.
+	(final_warning_record): New structure.
+	(final_warning_records): New static variable.
+	(possible_polymorphic_call_targets): Cleanup handling of speculative info;
+	do not build speculation when user do not care; record info about warnings
+	when asked for.
+	(add_decl_warning): New function.
+	(type_warning_cmp): New function.
+	(decl_warning_cmp): New function.
+	(ipa_devirt): Handle -Wsuggest-final-methods and -Wsuggest-final-types.
+	(gate): Enable pass when warnings are requested.
+	* common.opt (Wsuggest-final-types, Wsuggest-final-methods): New options.
+
 2014-08-02  Trevor Saunders  <tsaunders@mozilla.com>
 
 	* hash-map.h (default_hashmap_traits::mark_key_deleted):

gcc/common.opt

@@ -651,6 +651,14 @@ Wsuggest-attribute=noreturn
 Common Var(warn_suggest_attribute_noreturn) Warning
 Warn about functions which might be candidates for __attribute__((noreturn))
 
+Wsuggest-final-types
+Common Var(warn_suggest_final_types) Warning
+Warn about C++ polymorphic types where adding final keyword would improve code quality
+
+Wsuggest-final-methods
+Common Var(warn_suggest_final_methods) Warning
+Warn about C++ virtual methods where adding final keyword would improve code quality
+
 Wsystem-headers
 Common Var(warn_system_headers) Warning
 Do not suppress warnings from system headers

gcc/doc/invoke.texi

@@ -271,6 +271,7 @@ Objective-C and Objective-C++ Dialects}.
 -Wstack-protector -Wstack-usage=@var{len} -Wstrict-aliasing @gol
 -Wstrict-aliasing=n @gol -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
 -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{]} @gol
+-Wsuggest-final-types @gol -Wsuggest-final-methods @gol
 -Wmissing-format-attribute @gol
 -Wswitch  -Wswitch-default  -Wswitch-enum -Wswitch-bool -Wsync-nand @gol
 -Wsystem-headers  -Wtrampolines  -Wtrigraphs  -Wtype-limits  -Wundef @gol
@@ -4193,6 +4194,25 @@ case, and some functions for which @code{format} attributes are
 appropriate may not be detected.
 @end table
 
+@item -Wsuggest-final-types
+@opindex Wno-suggest-final-types
+@opindex Wsuggest-final-types
+Warn about types with virtual methods where code quality would be improved
+if the type was declared with C++11 final specifier, or, if possible,
+declared in anonymous namespace. This allows GCC to devritualize more aggressively
+the polymorphic calls. This warning is more effective with link time optimization,
+where the information about the class hiearchy graph is more complete.
+
+@item -Wsuggest-final-methods
+@opindex Wno-suggest-final-methods
+@opindex Wsuggest-final-methods
+Warn about virtual methods where code quality would be improved if the method
+was declared with C++11 final specifier, or, if possible, its type was declared
+in the anonymous namespace or with final specifier. This warning is more
+effective with link time optimization, where the information about the class
+hiearchy graph is more complete. It is recommended to first consider suggestins
+of @option{-Wsuggest-final-types} and then rebuild with new annotations.
+
 @item -Warray-bounds
 @opindex Wno-array-bounds
 @opindex Warray-bounds
@@ -9622,7 +9642,7 @@ before applying @option{--param inline-unit-growth}.  The default is 10000.
 @item inline-unit-growth
 Specifies maximal overall growth of the compilation unit caused by inlining.
 The default value is 30 which limits unit growth to 1.3 times the original
-size. Cold functions (either marked cold via an attribibute or by profile
+size. Cold functions (either marked cold via an attribute or by profile
 feedback) are not accounted into the unit size.
 
 @item ipcp-unit-growth

gcc/testsuite/ChangeLog

+2014-08-01  Jan Hubicka  <hubicka@ucw.cz>
+
+	* g++.dg/warn/Wsuggest-final.C: New testcase.
+	* g++.dg/ipa/devirt-34.C: Fix.
+
 2014-08-02  Marek Polacek  <polacek@redhat.com>
 
 	PR c/59855

gcc/testsuite/g++.dg/ipa/devirt-34.C

@@ -2,6 +2,9 @@
 /* { dg-options "-O2 -fdump-ipa-devirt"  } */
 struct A {virtual int t(){return 42;}};
 struct B:A {virtual int t(){return 1;}};
+
+struct A aa;
+struct B bb;
 int
 t(struct B *b)
 {

gcc/testsuite/g++.dg/warn/Wsuggest-final.C

+// { dg-do compile }
+// { dg-options "-O2 -Wsuggest-final-types -Wsuggest-final-methods" }
+struct A { // { dg-warning "final would enable devirtualization of 4 calls" }
+virtual void a() {} // { dg-warning "final would enable devirtualization of 2 calls" }
+ virtual void b() {} // { dg-warning "final would enable devirtualization of 2 calls"  }
+};
+void
+t(struct A *a)
+{
+  a->a();
+  a->a();
+  a->b();
+  a->b();
+}

gcc/varpool.c

@@ -340,8 +340,16 @@ varpool_node::ctor_useable_for_folding_p (void)
 
   /* Variables declared 'const' without an initializer
      have zero as the initializer if they may not be
-     overridden at link or run time.  */
-  if (!DECL_INITIAL (real_node->decl)
+     overridden at link or run time.
+
+     It is actually requirement for C++ compiler to optimize const variables
+     consistently. As a GNU extension, do not enfore this rule for user defined
+     weak variables, so we support interposition on:
+     static const int dummy = 0;
+     extern const int foo __attribute__((__weak__, __alias__("dummy"))); 
+   */
+  if ((!DECL_INITIAL (real_node->decl)
+       || (DECL_WEAK (decl) && !DECL_COMDAT (decl)))
       && (DECL_EXTERNAL (decl) || decl_replaceable_p (decl)))
     return false;